Re: [PATCH 6/6] nohz: Use IPI implicit full barrier against rq->nr_running r/w

2014-06-10 Thread Frederic Weisbecker
On Tue, Jun 10, 2014 at 05:48:13PM +0200, Peter Zijlstra wrote: > On Tue, Jun 10, 2014 at 05:15:09PM +0200, Frederic Weisbecker wrote: > > + /* > > + * More than one running task need preemption. > > + * nr_running update is assumed to be visible > > + * after IPI is sent from wakers. >

Re: [PATCH 6/6] nohz: Use IPI implicit full barrier against rq->nr_running r/w

2014-06-10 Thread Peter Zijlstra
On Tue, Jun 10, 2014 at 05:15:09PM +0200, Frederic Weisbecker wrote: > + /* > + * More than one running task need preemption. > + * nr_running update is assumed to be visible > + * after IPI is sent from wakers. > + */ That looks like whitespace damage. pgpTOiSWwMldV.pgp De

[PATCH 6/6] nohz: Use IPI implicit full barrier against rq->nr_running r/w

2014-06-10 Thread Frederic Weisbecker
A full dynticks CPU is allowed to stop its tick when a single task runs. Meanwhile when a new task gets enqueued, the CPU must be notified so that it can restart its tick to maintain local fairness and other accounting details. This notification is performed by way of an IPI. Then when the target